The research program involves the definition and analysis of the behavioral characteristics of five mammalian species (lion tamarian, rufous elephant shrew, bush dog, crab-eating fox, maned wolf) exhibiting gradations in monogamy. A major goal is the determination of whether life history characteristics and the type of monogamy are predictably correlated. The species are being compared with respect to pair-bond strength through the observation of the agonistic and affiliative interactions of mated pairs during and after pair-bond formation, and during reproduction. The degree of sex-specific aggression is being examined. Sex differences in roles are being compared in the five species, especially male and female parental investment and territorial behavior, e.g. scent-marking. Parental tolerance towards maturing offspring is being tested by the establishment of nuclear families, and the contribution of older juvenile helpers to rearing younger siblings is being determined. The relative importance of parental aggression or within-sibling aggression in promoting dispersal is being investigated.